project freezes and black screen

hey, 

this is the second time that this happens.

in the middle of editing my project i press play but nothing happens which is an indicator that my project has now crashed. meaning, i can press anything, whether it'd be play, skip, skip to the end, nothing works. if i close and reopen the app, the video line is now black. now i can press play and i can hear the audio but the preview stays black which basically means i cant continue editing. i had to restart the project. and it happened again.. 

this has happened to me on multiple occasions but not always. 

but the longer you work on a project the more frustrating it is. anybody else ran into this problem on mobile?